One of the benefits of having a son that is a scholar of ancient warfare, from Alexander the Great to the Byzantine Empire to the Mongols, is that we can have wide ranging discussions on very deep topics. Of perennial interest to us: why do complex societies/civilizations collapse?
One of interesting working theories we have is that while complex societies can be in decay for a long period of time, they only collapse when its favored elites abandon it/betray it.
Here's an example from Roman history written by Joseph Tainter:
The Collapse of The [Western] Roman Empire
One outcome of diminishing returns to complexity is illustrated by the collapse of the Western Roman Empire. As a solar-energy based society which taxed heavily, the empire had little fiscal reserve. When confronted with military crises, Roman Emperors often had to respond by debasing the silver currency (Figure 4.2) and trying to raise new funds. In the third century A.D. constant crises forced the emperors to double the size of the army and increase both the size and complexity of the government. To pay for this, masses of worthless coins were produced, supplies were commandeered from peasants, and the level of taxation was made even more oppressive (up to two-thirds of the net yield after payment of rent). Inflation devastated the economy. Lands and population were surveyed across the empire and assessed for taxes. Communities were held corporately liable for any unpaid amounts. While peasants went hungry or sold their children into slavery, massive fortifications were built, the size of the bureaucracy doubled, provincial administration was made more complex, large subsidies in gold were paid to Germanic tribes, and new imperial cities and courts were established. With rising taxes, marginal lands were abandoned and population declined. Peasants could no longer support large families. To avoid oppressive civic obligations, the wealthy fled from cities to establish self-sufficient rural estates. Ultimately, to escape taxation, peasants voluntarily entered into feudal relationships with these land holders. A few wealthy families came to own much of the land in the western empire, and were able to defy the imperial government. The empire came to sustain itself by consuming its capital resources; producing lands and peasant population (Jones 1964, 1974; Wickham 1984; Tainter 1988, 1994b). The Roman Empire provides history's best-documented example of how increasing complexity to resolve problems leads to higher costs, diminishing returns, alienation of a support population, economic weakness, and collapse. In the end it could no longer afford to solve the problems of its own existence.
A more recent example of this is how the bureaucratic elites of the former Soviet Union, turned on the system and quickly gutted it through privatization, when their privileges were reduced. An accelerant of the process was the availability of an external financial system to deposit the newly looted wealth.
The big question for those of us in the US/EU is whether we are seeing this process at work in our system. Are the government/business elites turning against the system?